Self-Assembly and -Cross-Linking Lamellar Films by Nanophase Separation with Solvent-Induced Anisotropic Structural Changes.

Abstract

In this study, we have prepared thermally and chemically stable lamellar polymer films via humid annealing. The amphiphilic polymer poly(N-dodecyl acrylamide-stat-3-(trimethoxysilyl)propyl acrylate) [p(DDA/TMSPA)] forms a self-assembled lamellar structure via annealing at 60 °C under 98% relative humidity (humid annealing) due to nanophase separation between the hydrophobic dodecyl side and main chains with the amide groups that contain adsorbed water. Moreover, a self-cross-linking reaction of TMSPA proceeds during the humid annealing. As a result, the lamellar films maintain their structure even when annealed above their glass-transition temperature. On the other hand, the films swell when immersed in toluene. The highly ordered lamellar structure collapses due to the swelling but can be re-established by subsequent humid annealing. A multilayer freestanding film can be exfoliated via sonication in toluene. The exfoliated multilayer films initially form a dome-shaped structure, which is converted to a plate-shaped structure upon humid annealing. In their entirety, these results reveal that the molecular-scale movement associated with the formation of the lamellar structure induces a macroscopic structural change. Consequently, p(DDA/TMSPA) can be considered as a new stimulus-responsive polymer.